There are presently on the market a number of systems for treating and recycling waste water. Present state of the art systems that are available to the small industrial waste stream generator is deficient in its ability to consistently produce clean water of sufficient quality that it can be recycled for additional industrial applications. The initial high cost of purchasing many of these systems is beyond the economic limits of many small businesses making cost effective compliance to environmental regulations an impossibility. Most of the water treatment and recycling systems presently available do not address all of the problems associated with industrial waste management wherein the waste water is generally contaminated by a combination of sources.
These remarks are particularly applicable to systems for cleaning equipment such as vehicle fleets of buses, truck tractors and trailers, vehicles for the construction industry and installations for washing airplanes it airports.
Presently, there are two primary methods or technologies available and employed by small commercial/industrial waste stream generators in removing solids and contaminants from waste effluents. Mechanical separation systems account for the majority of equipment used in small waste water treatment applications. These systems can be as simple as small in-line oil/water separators to highly complex filtration units utilizing membrane and multimedia filters. These systems rely upon a mechanical process to separate or screen solids or oil based contaminants from aqueous solutions.
The second technology involves the use of chemical precipitation and is generally reserved for applications involving the removal of heavy metals from plating and other metal working applications. In this process, positive and negative charged polymers are injected into a waste stream. Polymers attract soluble metals and other soil particles forming larger particles called "floc" which, because of their increased mass and weight, precipitate or settle to the bottom allowing the clarified water to remain at the top.
For the small waste stream generator, chemical precipitation is often performed in a batch treatment tank. The waste water is pumped into the tank and polymers are added and thoroughly mixed. The solids created by the flocculation process are pumped from the bottom of the tank and the clear or clarified water is decanted from the upper portion of the tank. The accumulated solids are usually processed through a filter press which removes excess water and reduces volume prior to off-site disposal.
For larger waste stream generators, inclined-plate clarifiers are often utilized which allows for a continuous flow precipitation process. These systems are generally quite large, expensive and require a trained technical staff to ensure proper operation. The solids produced by this process are normally reduced using a filter press.
Chemical precipitation systems have the ability to remove a wide range of solids and contaminants from waste streams. In the plating industry, it is not uncommon to treat waste influents with metal content exceeding 2000 ppm and produce clarified effluent with residual metals of less than 1 ppm. The primary drawback to this form of waste water treatment is that the process is highly susceptible to changes in the chemical makeup of the stream. Slight changes cause imbalances in the chemistry that will disrupt the precipitation and clarification process and normally requires constant monitoring by a technical staff. For these reasons, precipitation systems are utilized primarily by large waste water stream generators, high tech industries and firms generating contaminated waste effluent that can only be treated using this technology.
Filtration systems account for the largest percentage of all types of water treatment units employed by small industrial waste stream generators. Coupled with oil/water separators and mechanical oil skimming devices, filtration systems are used in all types of industrial cleaning effluents. Unfortunately, with the enforcement of the new clean water discharge regulations, the majority of these filtration systems do not adequately reduce contamination levels to acceptable discharge limits or produce water of high enough quality that it can be economically recycled.
U. S. Pat. No. 5,013,435 to Rider et al discloses a combination settling and chemical treatment system in which the water is passed upward through several zones. Tile first zone is an array of inclined tubes. The upper zones of are trays of various agents selected to precipitate ionic pollutants that are then removed by filtration.
U.S. Pat. No. 5,571,336 to Wurzburger et al discloses a base solution for cleaning aluminum made from a solution of CaO added to sulfuric acid.
Various disclosures teach methods for aiding in the precipitation of pollutants from liquids. For example, U.S. Pat. No. 5,380,430 to Overton et al discloses a magnetizing apparatus for treatment of fluids.
Common problems that are often experienced by companies using commercial filtration equipment for the treatment of industrial effluents include the following:
1. Recycled water is not clean, looks like "gray" water, will not consistently produce clean recyclable water. PA0 2. Recycled water can have a strong "rotten egg" odor (H.sub.2 S). PA0 3. Systems have a high purchase price. PA0 4. System require too much maintenance and management of the system is labor intensive. PA0 5. Systems do not provide for convenient disposal of sludge. PA0 6. Spent filter cartridges become hazardous materials requiring costly disposal. PA0 7. Expensive to operate.